Pinocembrin has a chemical name of 2,3-Dihydro-5,7-dihydroxy-2-phenyl-4H-1-benzopyran-4-one. Pinocembrin is a flavanone compound having one chiral center in its chemical structure. Natural pinocembrin has a steric structure of S-configuration and a specific rotation [α]D15 of −45.3 (c, 0.9, acetone as solvent). Pinocembrin can be separated from propolis as well as plants such as Pinus cembra, Eucalyptus sieberi, Alnus sieboldiana in a relatively low level. Accordingly, the complete synthesis thereof has been studied in the art and pinocembrin in form of racemate can be prepared in large scale (DUAN Yabo, et al., Chinese Journal of Medicinal Chemistry, 16(6): 342-346, 2006).
Pinocembrin has one chiral carbon in its molecule and thus has a pair of enantiomers i.e., (R)-pinocembrin and (S)-pinocembrin. Natural pinocembrin is (S)-pinocembrin, but its content in plants is very low and thus can not be obtained in large scale, whereas the studies on biological activities of (R)-pinocembrin are not found yet. In addition, pinocembrin has not a salt-forming acidic or basic group in its structure, so that the optical resolution of pinocembrin can not be performed by a conventional method of forming diastereomer salts. Currently, none of other methods such as crystallization, mechanical method or selective adsorption is found suitable for the resolution.
Therefore, there remains a need for a method for resolution of racemic pinocembrin to obtain a pinocembrin enantiomer with single configuration.